Investigation of pre-treatment techniques to improve membrane performance in real textile wastewater treatment

Membrane technology has a significant role in textile wastewater treatment considering the modular design of the membrane processes that enables to conceive a complete treatment scheme. The study presents a comparative study of microfiltration (MF) (0.2 µm and 0.05 µm), ultrafiltration (UF), ozonation (0.1, 0.2 g/L ozone), ultraviolet (UV) irradiation and titanium dioxide (TiO₂) (0.05, 0.15, 0.3, 0.5 g/L TiO₂) and zeolite adsorption (125, 250, 500 mL/min flow rates) processes as pre-treatment prior to nanofiltration (NF) and reverse osmosis (RO) membranes for the treatment of real textile washing wastewater (WW). Experiments demonstrated that the applied pre-treatment methods enhanced the flux performance of NF270 and RO membranes except zeolite adsorption. By evaluation of all pre-treatment alternatives, it was seen that the best chemical oxygen demand (COD) removal efficiency (41%) was achieved with MF0.05 membrane. The highest conductivity removal efficiencies were obtained by UV/TiO₂ application and with ozonation process the colour of the wastewater was removed at a performance of 80.5%, that was the highest among all pre-treatment applications. Based on the permeate flux and quality, the best pre-treatment method was selected as MF membrane with a pore size of 0.05 µm. Best conductivity removal efficiency was obtained by MF0.05 + XLE membrane combination at 93.6%. Also, considerably high COD removals were achieved with pre-treated NF and RO combinations together with a significant colour elimination (> 98%). In this study, it is aimed to create an efficient system that can be applied in real textile wastewater treatment by creating a combined treatment process.